1. Field of the Invention
The present invention relates generally to an image sensing system, and more particularly, to an image sensing system equipped with an interface between an image sensing apparatus, which generates image data, and a computer machinery which then receives the image data.
2. Description of the Related Art
To enter image data into a computer machinery (such as personal computers and word processors), an image sensing apparatus is connected to the computer machinery. As an example, the image sensing apparatus can be an image scanner or a video camera. In the case of an image scanner, the surface of a target original text is scanned to obtain image data. In many cases, the image sensing apparatus is equipped with a CCD (Charge Coupled Device) solid state image sensing device having a plurality of light-receiving pixels to receive moving pictures. The image sensing apparatus and the computer machinery are connected by an expansion circuit board called xe2x80x9cvideo capture unitxe2x80x9d. This video capture unit converts image data output from the image sensing apparatus to data which is suitable for use in the computer machinery. The converted data is stored in a memory incorporated in the computer machinery.
As shown in FIG. 1, a video capture unit 110 is provided between an image sensing apparatus 100 and a personal computer 120. The video capture unit 110 has an A/D converter 111, a frame memory 112, a sync detector 113, a timing controller 114, and an interface circuit 115.
The A/D converter 111 executes analog-to-digital conversion on analog image signal Y1(t) from the image sensing apparatus 100 in synchronism with the signal output operation of the CCD to thereby produce digital image data. This digital image data is produced for each light-receiving pixel of the CCD. The frame memory 112 stores the image data from the A/D converter 111 screen by screen. A dual port type RAM capable of accomplishing simultaneous writing and reading of image data is used for this frame memory 112. The sync detector 113 detects a sync signal included in the image signal Y1(t) from the image sensing apparatus 100 and produces a timing pulse signal associated with vertical scanning and horizontal scanning.
The timing controller 114 receives the timing pulse signal from the sync detector 113 and a read instruction signal, which is supplied from the personal computer 120 via the interface circuit 115. The timing controller 114 sends a control signal to the A/D converter 111 in response to the timing pulse signal. The A/D converter 111 operates in synchronism with the CCD in accordance with the control signal. Under this control, the A/D converter 111 converts the image signal Y1(t), supplied from the image sensing 100, to digital image data pixel by pixel.
In accordance with the timing pulse signal and the read instruction signal, the timing controller 114 supplies write and read timing control signals for image data to the frame memory 112. The timing controller 114 supplies a transfer instruction signal to the interface circuit 115 to instruct the transfer of the image data from the frame memory 112 to the personal computer 120. At the same time, the image data is stored in the frame memory 112 screen by screen, the interface circuit 115 reads image data from the frame memory 112 screen by screen and transfers the image data to the personal computer 120. The timing controller 114 sends an interruption signal to the interface circuit 115, which in turn sends the interruption signal to the personal computer 120.
The personal computer 120 repeats data processing such as receiving of image data, various arithmetic operations, access to a frame memory, and screen display control in a time-sharing manner in accordance with a command supplied through the keyboard and a command issued by the operation program. It is difficult for the personal computer 120, which performs such complicated processing, to continuously and rapidly receive image data in response to the operation of the image sensing apparatus 100. Image sensing apparatuses which conform to the general television forms, such as the NTSC standards and PAL standards, output several tens of frames of image data per second. Ordinary personal computers can however receive only several frames of image data per second.
The video capture unit 110 controls writing of data to the frame memory 112 in such a manner that a part of image data is read from the frame memory 112 and is transferred to the personal computer 120. For this writing control, the video capture unit 110 requires the A/D converter 111 to be fast and the frame memory 112 to have a large capacity. This requirement inevitably increases the cost of the video capture unit 110 and eventually increases the cost of the image sensing system which uses the video capture unit 110.
To improve operation and reduce the cost of such an image sensing system, the operation of the image sensing apparatus may be designed to match the operation of a computer machinery. For example, Japanese Patent Laid Open No. 7-87404 discloses an image sensing system which is designed so that the individual operation timings of an image sensing apparatus associated with the vertical and horizontal scans are controlled by a computer machinery. This image sensing system can directly supply image data to a computer machinery from the image sensing device without using any video capture unit. However, this design puts a large load on the computer machinery which controls the operation timings of the image sensing apparatus, thus making it difficult to increase the transfer speed of image data.
Broadly speaking, the present invention relates to an image sensing system designed to not only improve performance (e.g., transfer speed of image data) but also contribute to reducing the cost which is associated with the connection between a computer machinery and an image sensing apparatus.
The present invention can be implemented in numerous ways including as a system, an apparatus and a method. Several embodiments of the invention are detailed below.
As an image sensing system suitable for interfacing with a computer machinery, an embodiment of the invention includes: a solid state image sensing device having a plurality of light-receiving pixels for receiving light reflected from a target object to produce information charges and retain the information charges, the plurality of light-receiving pixels being arranged in a matrix form; a driver for driving the solid state image sensing device in accordance with vertical and horizontal scan timings to cause the solid state image sensing device to produce an analog image signal in proportion to an amount of the information charges retained in the light-receiving pixels and output the analog image signal line by line; a timing controller, connected to the driver, for setting the vertical and horizontal scan timings of the solid state image sensing device to be driven by the driver; an analog signal processor, connected to the solid state image sensing device, for performing signal processing on the analog image signal to produce a signal-processed analog image signal; an A/D converter, connected to the analog signal processor, for performing analog-to-digital conversion on the signal-processed analog image signal to produce a digital image signal; a digital signal processor, connected to the A/D converter, for performing signal processing on the digital image signal to produce image data for each pixel; a line memory circuit, connected to the digital signal processor, for continuously storing the image data; and an interface controller, connected to the line memory circuit, for reading the image data from the line memory circuit and outputting the image data. Preferably, the solid state image sensing device, the driver, the analog signal processor and the A/D converter constitute a camera unit, and the digital signal processor, the line memory circuit and the interface controller are incorporated in the computer machinery in such a way as to be connectable to the camera unit.
As an image sensing system suitable for interfacing with a computer machinery, another embodiment of the invention includes: a solid state image sensing device having a plurality of light-receiving pixels for receiving light reflected from a target object to produce information charges and retain the information charges, the plurality of light-receiving pixels being arranged in a matrix form; a driver for driving the solid state image sensing device in accordance with vertical and horizontal scan timings to cause the solid state image sensing device to produce an analog image signal in proportion to an amount of the information charges retained in the light-receiving pixels and output the analog image signal line by line; a timing controller, connected to the driver, for setting the vertical scan timing of the solid state image sensing device to be driven by the driver in accordance with a given period and for setting the horizontal scan timing of the solid state image sensing device in response to a line feed trigger supplied from the computer machinery; an analog signal processor, connected to the solid state image sensing device, for performing signal processing on the analog image signal to produce a signal-processed analog image signal; an A/D converter, connected to the analog signal processor, for performing analog-to-digital conversion on the signal-processed analog signal data to produce digital image signal; a digital signal processor, connected to the A/D converter, for performing signal processing on the digital image signal to produce image data for each pixel; a line memory circuit, connected to the digital signal processor, for continuously storing the image data line by line; and an interface controller, connected to the line memory circuit, for reading the image data from the line memory circuit and outputting the image data.
As an image sensing system suitable for interfacing with a computer machinery, yet another embodiment of the invention includes: a solid state image sensing device having a plurality of light-receiving pixels for receiving light reflected from a target object to produce information charges and retain the information charges, the plurality of light-receiving pixels being arranged in a matrix form; a driver for driving the solid state image sensing device in accordance with vertical and horizontal scan timings to cause the solid state image sensing device to produce an analog image signal in proportion to an amount of the information charges retained in the light-receiving pixels and output the analog image signal; a timing controller, connected to the driver, for setting the vertical and horizontal scan timings of the solid state image sensing device to be driven by the driver; an analog signal processor, connected to the solid state image sensing device, for performing signal processing on the analog image signal to produce a signal-processed analog image signal; an A/D converter, connected to the analog signal processor, for performing analog-to-digital conversion on the signal-processed analog image signal to produce a digital image signal; a digital signal processor, connected to the A/D converter, for performing signal processing on the digital image signal to produce image data for each pixel; a line memory circuit, connected to the digital signal processor, for continuously storing the image data line by line; a memory controller, connected to the line memory circuit, for controlling the line memory circuit in such a manner that the image data is written in the line memory circuit at a timing synchronous with the signal processing of the digital signal processor and the image data is read from the line memory circuit in accordance with a predetermined timing; and an interface controller, connected to the line memory circuit, for receiving the image data read from the line memory circuit and outputting the received image data.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principals of the invention.